1. Field of the Invention
The present invention relates generally to photosensitive materials, and particularly to those materials sensitive to exposure to ultraviolet light.
2. Description of the Prior Art
Photosensitive compositions for the detection and indication of ultraviolet light are well known. More particularly, a series of U.S. Patents held by Lyman Chalkley discusses a system utilizing certain photosensitive substances identified as leuco-cyanides of aminotriarylmethane dyes. Chalkley conducted indepth investigations with these dyes, and proposed a series of compositions, containing the leuco-cyanide dyes, with various activators, such as carboxylic acids, amides, mercurous derivatives and silver derivatives. In other instances, Chalkley proposed to heat the dye-cyanide complex together with its activator, to a point of fusion, at which exposure to ultraviolet radiation was made. The foregoing and other variations on this investigation are set forth in U.S. Patents, and a partial listing is provided herein. U.S. Pat. Nos. 2,325,038; 2,366,179; 2,441,561; 2,528,496; 2,676,887; 2,829,052; 2,829,148; 2,839,542; 2,839,543; 2,844,465; 2,855,303; 2,855,304; 2,877,166; 2,936,235; 3,122,438; and 3,407,065; are referred to as representative.
A full review of the Chalkley publications, and other publications relating to this subject, indicates that the leuco-cyanides exhibited certain inadequacies in operation, that rendered them incapable of general acceptance for the purposes of detecting and quantifying ultraviolet radiation with scientific accuracy. In particular, the leuco-cyanides, regardless of their specific composition, all appeared to require the presence of an activator compound for their operations. Without this activator compound, either the leuco-cyanides would not give the color reaction expected upon exposure to ultraviolet radiation, or would give such color reaction and later exhibit loss of intensity and fading. In either event, the instability of the leuco-cyanide dye system rendered it unreliable for widespread acceptance and use.
The measurement of electromagnetic wave energy, in the area of X-rays, gamma rays and ultraviolet light has become increasingly important, from the standpoint of theoretical scientific investigation, as well as practical attention to personal health. It is therefore important to be able to quantitatively delineate radiation in this portion of the spectrum with speed and precision, and a need therefore exists for a system that can be inexpensively and easily used in a scientifically reproducible, and therefore reliable manner.